This invention relates to make-up air equipment. More specifically, this invention relates to equipment which provides make-up air and the control of such equipment.
Make-up air equipment supplies additional outside air to a building space. Make-up air is needed when an exhaust producing appliance within the building is operated. This make-up air equipment keeps the building from becoming depressurized. If depressurization of the building occurs, potentially dangerous situations may exist. Most importantly, spillage and back drafting of combustion by-products can occur--a very hazardous situation. This is generally true of all fossil fuel appliances like furnaces, water heaters, and wood burning equipment, etc.
In addition to the potentially hazardous situation mentioned above, an imbalance between the indoor and outdoor pressure can create uncomfortable conditions for the building occupants and can negatively impact the building structure. As is well known, air will move from spaces with a higher pressure to spaces with a lower pressure. Small openings in the building envelope allow for air to move through the wall to the lower pressure side. Depending on the indoor and outdoor temperature and dew point conditions, this may lead to condensation occurring within the wall and eventually to a degradation of the building structure. Imbalanced air pressures can also make doors and windows difficult to open and close and, in some cases prevent them from being held open or closed as desired. Consequently, it is desirable to utilize appropriate equipment to maintain indoor pressure equal to outdoor pressure.
Make-up air equipment generally consists of a fan and damper arrangement, sometimes utilizing a heater to condition outdoor air prior to delivery indoors. However, a control system does not presently exist for automatically adjusting the amount of make-up air to maintain neutral indoor air pressure (relative to outdoors). As a result, make-up air systems typically are manually controlled by simply turning a switch on or off. Such systems are often not turned on when needed, and do not respond to variable demand when, for example, multiple exhausting devices are used simultaneously. Other present make-up air systems may be interlocked with exhausting devices, but still lack the ability to respond to variable demand.